Aerosol-generating system having a heater assembly and a cartridge for an aerosol-generating system having a fluid permeable heater assembly

ABSTRACT

An aerosol-generating system including a liquid storage portion is provided, the portion including a rigid housing holding a liquid aerosol-forming substrate, the housing having an opening and a fluid permeable heater assembly including a plurality of electrically conductive filaments, wherein the fluid permeable heater assembly is fixed to the housing and extends across the opening of the housing. The provided heater assembly that extends across an opening of a liquid storage portion allows for a robust construction that is relatively simple to manufacture and allows for a large contact area between the heater assembly and liquid aerosol-forming substrate. The heater assembly may be substantially flat, allowing for simple manufacture.

The present invention relates to aerosol-generating systems thatcomprise a heater assembly that is suitable for vapourising a liquid. Inparticular, the invention relates to handheld aerosol-generatingsystems, such as electrically operated smoking systems.

One type of aerosol-generating system is an electrically operatedsmoking system. Handheld electrically operated smoking systemsconsisting of a device portion comprising a battery and controlelectronics, and a cartridge portion comprising a supply ofaerosol-forming substrate, and an electrically operated vapouriser, areknown. A cartridge comprising both a supply of aerosol-forming substrateand a vapouriser is sometimes referred to as a “cartomiser”. Thevapouriser typically comprises a coil of heater wire wound around anelongate wick soaked in liquid aerosol-forming substrate. The cartridgeportion typically comprises not only the supply of aerosol-formingsubstrate and an electrically operated vapouriser, but also amouthpiece, which the user sucks on in use to draw aerosol into theirmouth.

However, this arrangement has the drawback that the cartridges arerelatively expensive to produce. This is because manufacturing the wickand coil assembly is difficult. Also, the electrical contacts betweenthe coil of heater wire and the electrical contacts through whichelectrical current is delivered from the device portion must bedelicately handled during manufacture. Furthermore, these cartridgesinclude a mouthpiece portion in order to protect the delicate wick andcoil assembly during transport. But the inclusion of a complete androbust mouthpiece in each cartridge means that each cartridge has a highmaterial cost.

It would be desirable to provide a heater assembly suitable for anaerosol-generating system, such as a handheld electrically operatedsmoking system, that is inexpensive to produce and is robust. It wouldbe further desirable to provide a heater assembly that is more efficientthan prior heater assemblies in aerosol-generating systems.

In a first aspect there is provided an aerosol-generating systemcomprising:

a liquid storage portion comprising a housing holding a liquidaerosol-forming substrate, the housing having an opening; and

a fluid permeable heater assembly comprising a plurality of electricallyconductive filaments, wherein the fluid permeable heater assembly isfixed to the housing and extends across the opening of the housing.

The provision of a heater assembly that extends across an opening of aliquid storage portion allows for a robust construction that isrelatively simple to manufacture. This arrangement allows for a largecontact area between the heater assembly and liquid aerosol-formingsubstrate. The housing may be a rigid housing. As used herein “rigidhousing” means a housing that is self-supporting. The rigid housing ofthe liquid storage portion preferably provides mechanical support to theheater assembly. The heater assembly may be substantially flat allowingfor simple manufacture. As used herein, “substantially flat” meansformed initially in a single plane and not wrapped around or otherconformed to fit a curved or other non-planar shape. Geometrically, theterm “substantially flat” electrically conductive filament arrangementis used to refer to an electrically conductive filament arrangement thatis in the form of a substantially two dimensional topological manifold.Thus, the substantially flat electrically conductive filamentarrangement extends in two dimensions along a surface substantially morethan in a third dimension. In particular, the dimensions of thesubstantially flat filament arrangement in the two dimensions within thesurface is at least 5 times larger than in the third dimension, normalto the surface. An example of a substantially flat filament arrangementis a structure between two substantially imaginary parallel surfaces,wherein the distance between these two imaginary surfaces issubstantially smaller than the extension within the surfaces. In someembodiments, the substantially flat filament arrangement is planar. Inother embodiments, the substantially flat filament arrangement is curvedalong one or more dimensions, for example forming a dome shape or bridgeshape.

The term “filament” is used throughout the specification to refer to anelectrical path arranged between two electrical contacts. A filament mayarbitrarily branch off and diverge into several paths or filaments,respectively, or may converge from several electrical paths into onepath. A filament may have a round, square, flat or any other form ofcross-section. A filament may be arranged in a straight or curvedmanner.

The term “filament arrangement” is used throughout the specification torefer to an arrangement of one or preferably a plurality of filaments.The filament arrangement may be an array of filaments, for examplearranged parallel to each other. Preferably, the filaments may form amesh. The mesh may be woven or non-woven.

A flat heater assembly can be easily handled during manufacture andprovides for a robust construction.

The system may advantageously comprise a device and a cartridge that isremovably coupled to the device, wherein the liquid storage portion andheater assembly are provided in the cartridge and the device comprises apower supply. The cartridge may be manufactured at low cost, in areliable and repeatable fashion. As used herein, the cartridge being“removably coupled” to the device means that the cartridge and devicecan be coupled and uncoupled from one another without significantlydamaging either the device or the cartridge.

The system may be an electrically operated smoking system.

The electrically conductive filaments may lie in a single plane. Aplanar heater assembly can be easily handled during manufacture andprovides for a robust construction.

The electrically conductive filaments may define interstices between thefilaments and the interstices may have a width of between 10 μm and 100μm. Preferably the filaments give rise to capillary action in theinterstices, so that in use, liquid to be vapourised is drawn into theinterstices, increasing the contact area between the heater assembly andthe liquid.

The electrically conductive filaments may form a mesh of size between160 and 600 Mesh US (+/−10%) (i.e. between 160 and 600 filaments perinch (+/−10%)). The width of the interstices is preferably between 75 μmand 25 μm. The percentage of open area of the mesh, which is the ratioof the area of the interstices to the total area of the mesh ispreferably between 25% and 56%. The mesh may be formed using differenttypes of weave or lattice structures. Alternatively, the electricallyconductive filaments consist of an array of filaments arranged parallelto one another.

The mesh, array or fabric of electrically conductive filaments may alsobe characterised by its ability to retain liquid, as is well understoodin the art.

The electrically conductive filaments may have a diameter of between 10μm and 100 μm, preferably between 8 μm and 50 μm, and more preferablybetween 8 μm and 39 μm. The filaments may have a round cross section ormay have a flattened cross-section.

The area of the mesh, array or fabric of electrically conductivefilaments may be small, preferably less than or equal to 25 mm²,allowing it to be incorporated in to a handheld system. The mesh, arrayor fabric of electrically conductive filaments may, for example, berectangular and have dimensions of 5 mm by 2 mm. Preferably, the mesh orarray of electrically conductive filaments covers an area of between 10%and 50% of the area of the heater assembly. More preferably, the mesh orarray of electrically conductive filaments covers an area of between 15%and 25% of the area of the heater assembly. Sizing of the mesh, array orfabric of electrically conductive filaments 10% and 50% of the area, orless or equal than 25 mm2, reduces the amount of total power required toheat the mesh, array or fabric of electrically conductive filamentswhile still ensuring sufficient contact of the mesh, array or fabric ofelectrically conductive filaments to the liquid provided one or morecapillary materials to be volatilized.

The heater filaments may be formed by etching a sheet material, such asa foil. This may be particularly advantageous when the heater assemblycomprises an array of parallel filaments. If the heater assemblycomprises a mesh or fabric of filaments, the filaments may beindividually formed and knitted together. Alternatively, the heaterfilaments may be stamped from electrically conductive foil, as forexample stainless steel.

The filaments of the heater assembly may be formed from any materialwith suitable electrical properties. Suitable materials include but arenot limited to: semiconductors such as doped ceramics, electrically“conductive” ceramics (such as, for example, molybdenum disilicide),carbon, graphite, metals, metal alloys and composite materials made of aceramic material and a metallic material. Such composite materials maycomprise doped or undoped ceramics. Examples of suitable doped ceramicsinclude doped silicon carbides. Examples of suitable metals includetitanium, zirconium, tantalum and metals from the platinum group.Examples of suitable metal alloys include stainless steel, constantan,nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-,niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-and iron-containing alloys, and super-alloys based on nickel, iron,cobalt, stainless steel, Timetal®, iron-aluminium based alloys andiron-manganese-aluminium based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. The filaments may be coated withone or more insulators. Preferred materials for the electricallyconductive filaments are 304, 316, 304L, 316L stainless steel, andgraphite. Additionally, the electrically conductive filament arrangementmay comprise combinations of the above materials. A combination ofmaterials may be used to improve the control of the resistance of thesubstantially flat filament arrangement. For example, materials with ahigh intrinsic resistance may be combined with materials with a lowintrinsic resistance. This may be advantageous if one of the materialsis more beneficial from other perspectives, for example price,machinability or other physical and chemical parameters. Advantageously,a substantially flat filament arrangement with increased resistancereduces parasitic losses. Advantageously, high resistivity heatersallows more efficient use of battery energy. The battery energy isproportionally divided between the energy lost on the printed circuitboard and the contacts and energy delivered to the electricallyconductive filament arrangement. Thus the energy available for theelectrically conductive filament arrangement in the heater is higher thehigher the resistance of the electrically conductive filamentarrangement.

In an exemplary embodiment, a substantially flat filament arrangementmay be constructed from two types of metal wires that are formed into awire mesh. In such an embodiment, preferably, high resistive wires areoriented in the direction of the flow of electric current, for example,wires made from a nickel chromium alloy. Accordingly, in this embodimentlow resistive wires are arranged substantially perpendicular to thewires with high electrical resistance. For example, the low resistivewires may be stainless steel wires. Advantageously, the relativelycheaper low resistance wires form the support for the wires with highelectrical resistance. In addition, wires with high electricalresistance typically are less malleable than stainless steel wires andcan thus not be manufactured easily into thin wires. Therefore, in suchan advantageous embodiment of the invention, the relatively thick wireswith high electrical resistance are combined with thin stainless steelwires of low electrical resistance with the added benefit that thethinner stainless steel wires improve the wetting of the substantiallyflat filament arrangement through the increased capillary forces.

Alternatively, the electrically conductive filament arrangement may beformed of carbon thread textile. Carbon thread textile has the advantagethat it is typically more cost efficient than metallic heaters with highresistivity. Further, a carbon thread textile is typically more flexiblethan a metallic mesh. Another advantage is that the contact between acarbon thread textile and a transport medium like a high releasematerial can be well preserved during construction of the fluidpermeable heater assembly.

A reliable contact between the fluid permeable heater assembly and atransport medium, like for example a capillary transport medium such asa wick made from fibres or a porous ceramic material, improves theconstant wetting of the fluid permeable heater assembly. Thisadvantageously reduces the risk of overheating of the electricallyconductive filament arrangement and inadvertent thermal decomposition ofthe liquid.

The heater assembly may comprise an electrically insulating substrate onwhich the filaments are supported. The electrically insulating substratemay comprise any suitable material, and is preferably a material that isable to tolerate high temperatures (in excess of 300 degrees Celsius)and rapid temperature changes. An example of a suitable material is apolyimide film, such as Kapton®. The electrically insulating substratemay have an aperture formed in it, with the electrically conductivefilaments extending across the aperture. The heater assembly maycomprise electrical contacts connected to the electrically conductivefilaments. For example, the electrical contacts may be glued, welded ormechanically clamped to the electrically conductive filamentarrangement. Alternatively the electrically conductive filamentarrangement may be printed on the electrically insulating substrate, forexample using metallic inks. In such an arrangement, preferably, theelectrically insulating substrate is a porous material, such that theelectrically conductive filament arrangement can be directly applied tothe surface of the porous material. Preferably, in such an embodimentthe porosity of the substrate functions as the “opening” of theelectrically insulating substrate through which a liquid may be drawntowards the electrically conductive filament arrangement.

The electrical resistance of the mesh, array or fabric of electricallyconductive filaments of the heater element is preferably between 0.3Ohms and 4 Ohms. More preferably, the electrical resistance of the mesh,array or fabric of electrically conductive filaments is between 0.5 Ohmsand 3 Ohms, and more preferably about 1 Ohm. The electrical resistanceof the mesh, array or fabric of electrically conductive filaments ispreferably at least an order of magnitude, and more preferably at leasttwo orders of magnitude, greater than the electrical resistance of thecontact portions. This ensures that the heat generated by passingcurrent through the heater element is localised to the mesh or array ofelectrically conductive filaments. It is advantageous to have a lowoverall resistance for the heater element if the system is powered by abattery. A low resistance, high current system allows for the deliveryof high power to the heater element. This allows the heater element toheat the electrically conductive filaments to a desired temperaturequickly.

The first and second electrically conductive contact portions may befixed directly to the electrically conductive filaments. The contactportions may be positioned between the electrically conductive filamentsand the electrically insulating substrate. For example, the contactportions may be formed from a copper foil that is plated onto theinsulating substrate. The contact portions may also bond more readilywith the filaments than the insulating substrate would.

Alternatively, the first and second electrically conductive contactportions may be integral with the electrically conductive filaments. Forexample, the heater element may be formed by etching a conductive sheetto provide a plurality of filaments between two contact portions.

The heater assembly may comprise at least one filament made from a firstmaterial and at least one filament made from a second material differentfrom the first material. This may be beneficial for electrical ormechanical reasons. For example, one or more of the filaments may beformed from a material having a resistance that varies significantlywith temperature, such as an iron aluminium alloy. This allows a measureof resistance of the filaments to be used to determine temperature orchanges in temperature. This can be used in a puff detection system andfor controlling heater temperature to keep it within a desiredtemperature range. Sudden changes in temperature may also be used as ameans to detect changes in air flow past the heater assembly resultingfrom a user puffing on the system.

The housing of the liquid storage portion advantageously contains acapillary material. A capillary material is a material that activelyconveys liquid from one end of the material to another. The capillarymaterial is advantageously oriented in the housing to convey liquid tothe heater assembly.

The capillary material may have a fibrous or spongy structure. Thecapillary material preferably comprises a bundle of capillaries. Forexample, the capillary material may comprise a plurality of fibres orthreads or other fine bore tubes. The fibres or threads may be generallyaligned to convey liquid to the heater. Alternatively, the capillarymaterial may comprise sponge-like or foam-like material. The structureof the capillary material forms a plurality of small bores or tubes,through which the liquid can be transported by capillary action. Thecapillary material may comprise any suitable material or combination ofmaterials. Examples of suitable materials are a sponge or foam material,ceramic- or graphite-based materials in the form of fibres or sinteredpowders, foamed metal or plastics material, a fibrous material, forexample made of spun or extruded fibres, such as cellulose acetate,polyester, or bonded polyolefin, polyethylene, terylene or polypropylenefibres, nylon fibres or ceramic. The capillary material may have anysuitable capillarity and porosity so as to be used with different liquidphysical properties. The liquid has physical properties, including butnot limited to viscosity, surface tension, density, thermalconductivity, boiling point and vapour pressure, which allow the liquidto be transported through the capillary device by capillary action.

The capillary material may be in contact with the electricallyconductive filaments. The capillary material may extend into intersticesbetween the filaments. The heater assembly may draw liquidaerosol-forming substrate into the interstices by capillary action. Thecapillary material may be in contact with the electrically conductivefilaments over substantially the entire extent of the aperture. In oneembodiment the capillary material in contact with the electricallyconductive filament arrangement may be a filamentary wick. Preferably,the filamentary wick has a first section and a second section, whereinthe first section is arranged substantially perpendicular to theelectrically conductive filament arrangement, reaching into the liquidstorage portion of the cartridge. Preferably, the second section of thefilamentary wick is arranged substantially in parallel to theelectrically conductive filament arrangement. Preferably, the filamentsof the filamentary wick are continuous from the first section of thefilamentary wick to the second section of the filamentary wick. Thisallows a quick transport of the liquid towards the electricallyconductive filament arrangement through the first section of thefilamentary wick and, at the same time, a quick distribution across theelectrically conductive filament arrangement through the second sectionof the filamentary wick. This allows advantageously a continuous wettingof the entire the electrically conductive filament arrangement. Acontinuous wetting can avoid overheating and prevent the inadvertentdecomposition of the liquid due to the overheating.

Preferably, the electrically conductive filament arrangement comprisesat least several filaments made of alloys or coated with films which aresensitive to presence of liquid such as water. This allows the detectionof wetting of the electrically conductive filament arrangement, forexample by connecting the sensitive wires to a circuit that monitorselectrical resistance of the wires and prevent the heater from workingor reduce an electrical current in case of detection of dry interface.This advantageously increases the safety of aerosol generating system.In one embodiment, the filaments that are used for detection of thewetting are stainless steel wires that are coated with Indium nitride(InN) or aluminium oxide (Al2O3) films. In use, a liquid like waterdepletes electrons from such film surfaces and preserves high electricalresistivity of the film up to the moment when film surface becomes dry.Then the resistivity drops rapidly. The drop in resistivity is bedetected by the connected electronic circuit.

Advantageously, the heater assembly and the capillary material may besized to have approximately the same area. As used here, approximatelymeans between that the heater assembly may be between 0-15% larger thanthe capillary material. The shape of the heater assembly may also besimilar to the shape of the capillary material such that the assemblyand the material substantially overlap. When the assembly and thematerial are substantially similar in size and shape, manufacturing canbe simplified and the robustness of the manufacturing process improved.As discussed below, the capillary material may include two or morecapillary materials including one or more layers of the capillarymaterial directly in contact with the mesh, array or fabric ofelectrically conductive filaments of the heater assembly in order topromote aerosol generation. The capillary materials may includematerials described herein.

At least one of the capillary materials may be of sufficient volume inorder to ensure that a minimal amount of liquid is present in saidcapillary material to prevent “dry heating”, which occurs ifinsufficient liquid is provided to the capillary material in contactwith the mesh, array or fabric of electrically conductive filaments. Aminimum volume of said capillary material may be provided in order toallow for between 20-40 puffs by the user. An average volume of liquidvolatilized during a puff of a length between 1-4 seconds is typicallybetween 1-4 mg of liquid. Thus, providing at least one capillarymaterial having a volume to retain between 20-160 mg of the liquidcomprising the liquid-forming substrate may prevent the dry heating.

The housing may contain two or more different capillary materials,wherein a first capillary material, in contact with the heater element,has a higher thermal decomposition temperature and a second capillarymaterial, in contact with the first capillary material but not incontact with the heater element has a lower thermal decompositiontemperature. The first capillary material effectively acts as a spacerseparating the heater element from the second capillary material so thatthe second capillary material is not exposed to temperatures above itsthermal decomposition temperature. As used herein, “thermaldecomposition temperature” means the temperature at which a materialbegins to decompose and lose mass by generation of gaseous by products.The second capillary material may advantageously occupy a greater volumethan the first capillary material and may hold more aerosol-formingsubstrate that the first capillary material. The second capillarymaterial may have superior wicking performance to the first capillarymaterial. The second capillary material may be cheaper than the firstcapillary material. The second capillary material may be polypropylene.

The first capillary material may separate the heater assembly from thesecond capillary material by a distance of at least 1.5 mm, andpreferably between 1.5 mm and 2 mm in order to provide a sufficienttemperature drop across the first capillary material.

The liquid storage portion may be positioned on a first side of theelectrically conductive filaments and an airflow channel positioned onan opposite side of the electrically conductive filaments to the liquidstorage portion, such that air flow past the electrically conductivefilaments entrains vapourised liquid aerosol-forming substrate. Inaddition to the electrical heater assembly that is located in closeproximity or in contact to the liquid transport medium, theaerosol-generating system may comprise at least one further electricalheater assembly in operational relationship with the liquid storageportion. A further electrical heater assembly in operationalrelationship with the liquid storage portion may increase the depletionof the liquid from liquid storage portion. This is particularlyadvantageous where the liquid storage portion comprises a high retentionmedium storing the liquid. It is advantageous to use a high retentionmedium to store liquid in the liquid storage portion. For example, theuse a high retention medium reduces the risk of spill. In case offailure or cracks of the housing of the cartridge spilled liquid couldlead to unintended contact with active electrical components andbiological tissues. However, as the liquid is attracted by wettabilityforces to the high retention medium surface, a substantial loss ofliquid is less likely if compared to free liquid filled tanks in case ofmechanical cracks in the cartridge housing. However, as the highretention medium will intrinsically retain at least some portion of theliquid, which in turn is not available for aerosolization.Advantageously, the provision of additional heating assemblies increasesthe ratio of the depletion of the liquid storage portion, that is, theratio between the amount of liquid removed from the liquid storageportion and the amount of liquid that cannot be removed from the liquidstorage portion.

Preferably, the further electrical heater assembly is located close tothe areas of the high retention medium that are less likely to bedepleted by the primary electrical heater assembly, for example, themost areas of the high retention medium that are most distant from thefirst electrical heater assembly. Preferably, the further electricalheater assembly is located in the bottom wall of the housing, that is,the wall that is opposite of the electrical heater assembly.Alternatively or in addition, the further electrical heater assembly islocated at a side wall of the housing.

Preferably, the further electrical heater assembly is controlled to beactivated only as needed, for example when a reduction of the liquidflow is detected. For example, the further electrical heater assemblymay be activated when a reduction in the wetting of the first electricalheater assembly is detected.

Alternatively or in addition, the housing has internally anon-cylindrical, for example a conical form, such that the wider sectionof the internal non-cylindrical form is directed towards the electricalheater assembly and the internal smaller section extends into anopposite direction. This allows for an increase of the relevance of thegravitational forces acting on the liquid to advance the liquid towardsthe electrical heater assembly, in particular where theaerosol-generating system is in a substantially horizontal orientation.A horizontal orientation is an orientation in which the electricalheater assembly is substantially on the same vertical level as theliquid storage portion. This horizontal orientation is typical duringthe use of the aerosol-generating system.

Alternatively or in addition, the cartridge comprising the electricalheater assembly and the housing is arranged in the aerosol-generatingsystem such that electrical heater assembly is arranged across theopening of the housing on the side of the liquid storage portion that isdistant from the mouthpiece of the aerosol-generating system. This maybe beneficial for the flow path of the aerosol within the aerosolgenerating system. For example, in a vertical arrangement of the aerosolgenerating system the mouthpiece is on the top and the housing isarranged up-side down, that is, the liquid is arranged above theelectrical heater assembly. In such an embodiment, capillary forces toadvance the liquid towards the electrical heater assembly are beassisted by the gravitational forces, instead of having to overcome thegravitational forces.

Preferably, the housing comprises two elements, wherein a first elementis a cap and a second element is a tank, wherein the cap closes thetank. Preferably, according to the invention, the cap comprises or is inclose contact with the heater assembly. Preferably, the tank comprisesthe liquid, and where present the first capillary material or both firstand second capillary materials. Preferably, the cap material is madefrom a material with a high thermal decomposition temperature, such asfor example polyetheretherketone (PEEK) or Kapton®. Preferably, the caphas a size sufficient to distance the tank from the heater assembly by adistance of at least 1.5 mm, and preferably between 1.5 mm and 2 mm inorder to provide a sufficient temperature drop across the cap.Advantageously, in such an embodiment, the tank material can be madefrom a more cost efficient material with a lower thermal decompositiontemperature, such as for example polyethylene or polypropylene.

An air inlet of the for example be arranged in a main housing of thesystem. Ambient air is directed into the system, passes the heatingelement at the distal end of the cartridge and entrains an aerosolcaused by heating the aerosol-forming substrate in the cartridge. Theaerosol containing air may then be guided along the cartridge between acartridge housing and a main housing to the downstream end of thesystem, where it is mixed with ambient air from the further flow route(either before or upon reaching the downstream end).

An inlet opening of the second channel arranged in a region of a distalend of a cartridge housing may also be provided in an alternative systemwhere a heating element is arranged at a proximal end of the cartridge.The second flow route may not only pass outside of the cartridge butalso through the cartridge. Ambient air then enters the cartridge at asemi-open wall of the cartridge, passes through the cartridge and leavesthe cartridge by passing though the heating element arranged at theproximal end of the cartridge. Thereby, ambient air may pass through theaerosol-forming substrate or through one or several channels arranged ina solid aerosol-forming substrate such that ambient air does not passthrough the substrate itself but in the channels next to the substrate.

For allowing ambient air to enter a cartridge, a wall of the cartridgehousing, preferably a wall opposite the heating element, preferably abottom wall, is provided with at least one semi-open inlet. Thesemi-open inlet allows air to enter the cartridge but no air or liquidto leave the cartridge through the semi-open inlet. A semi-open inletmay for example be a semi-permeable membrane, permeable in one directiononly for air but is air- and liquid-tight in the opposite direction. Asemi-open inlet may for example also be a one-way valve. Preferably thesemi-open inlets allow air to pass through the inlet only if specificconditions are met, for example a minimum depression in the cartridge ora volume of air passing through the valve or membrane.

Such one-way valves may, for example, be commercially available valves,such as for example used in medical devices, for example LMS MediflowOne-Way, LMS SureFlow One-Way or LMS Check Valves (crosses membranes).Suitable membranes to be used for a cartridge having an airflow passingthrough the cartridge, are for example vented membranes as used inmedical devices, for example Qosina Ref. 11066, vented cap withhydrophobic filter or valves as used in baby bottles. Such valves andmembranes may be made of any material suitable for applications inelectrically heated smoking systems. Materials suitable for medicaldevices and FDA approved materials may be used; for example Graphenehaving very high mechanical resistance and thermal stability within alarge range of temperatures. Preferably, valves are made of softresilient material for supporting a liquid-tight incorporation of theone or several valves into a wall of the container housing.

Letting ambient air pass through the substrate supports anaerosolization of the aerosol-forming substrate. During puffing, adepression occurs in the cartridge, which may activate the semi-openinlets. Ambient air then passes the cartridge, preferably a highretention or high release material (HRM) or a liquid, and crosses theheating element, thereby creating and sustaining aerosolization of theliquid, when the heating element sufficiently heats the liquid. Inaddition, due to the depression caused during puffing, a supply ofliquid in a transport material such as a capillary material to theheating element may be limited. An ambient airflow through the cartridgemay equalize pressure differences within the cartridge and therebysupport an unhindered capillary action towards the heating element.

A semi-open inlet may, in addition, or alternatively also be provided inone or several side walls of the cartridge housing. Semi-open inlets inside walls provide a lateral airflow into the cartridge towards the opentop end of the cartridge housing, where the heating element is arranged.Preferably, lateral airflows pass through the aerosol-forming substrate.

The system may further comprise electric circuitry connected to theheater assembly and to an electrical power source, the electriccircuitry configured to monitor the electrical resistance of the heaterassembly or of one or more filaments of the heater assembly, and tocontrol the supply of power to the heater assembly dependent on theelectrical resistance of the heater assembly or the one or morefilaments.

The electric circuitry may comprise a microprocessor, which may be aprogrammable microprocessor. The electric circuitry may comprise furtherelectronic components. The electric circuitry may be configured toregulate a supply of power to the heater assembly. Power may be suppliedto the heater assembly continuously following activation of the systemor may be supplied intermittently, such as on a puff-by-puff basis. Thepower may be supplied to the heater assembly in the form of pulses ofelectrical current.

The system advantageously comprises a power supply, typically a battery,within the main body of the housing. As an alternative, the power supplymay be another form of charge storage device such as a capacitor. Thepower supply may require recharging and may have a capacity that allowsfor the storage of enough energy for one or more smoking experiences;for example, the power supply may have sufficient capacity to allow forthe continuous generation of aerosol for a period of around six minutesor for a period that is a multiple of six minutes. In another example,the power supply may have sufficient capacity to allow for apredetermined number of puffs or discrete activations of the heaterassembly.

Preferably, the aerosol generating system comprises a housing.Preferably, the housing is elongate. The housing may comprise anysuitable material or combination of materials. Examples of suitablematerials include metals, alloys, plastics or composite materialscontaining one or more of those materials, or thermoplastics that aresuitable for food or pharmaceutical applications, for examplepolypropylene, polyetheretherketone (PEEK) and polyethylene. Preferably,the material is light and non-brittle.

Preferably, the aerosol-generating system is portable. Theaerosol-generating system may have a size comparable to a conventionalcigar or cigarette. The smoking system may have a total length betweenapproximately 30 mm and approximately 150 mm. The smoking system mayhave an external diameter between approximately 5 mm and approximately30 mm.

The aerosol-forming substrate is a substrate capable of releasingvolatile compounds that can form an aerosol. The volatile compounds maybe released by heating the aerosol-forming substrate.

The aerosol-forming substrate may comprise plant-based material. Theaerosol-forming substrate may comprise tobacco. The aerosol-formingsubstrate may comprise a tobacco-containing material containing volatiletobacco flavour compounds, which are released from the aerosol-formingsubstrate upon heating. The aerosol-forming substrate may alternativelycomprise a non-tobacco-containing material. The aerosol-formingsubstrate may comprise homogenised plant-based material. Theaerosol-forming substrate may comprise homogenised tobacco material. Theaerosol-forming substrate may comprise at least one aerosol-former. Theaerosol-forming substrate may comprise other additives and ingredients,such as flavourants.

In a second aspect, there is provided a cartridge for use in anelectrically operated aerosol-generating system, comprising:

a liquid storage portion comprising a housing holding a liquidaerosol-forming substrate, the housing having an opening; and

a fluid permeable heater assembly comprising a plurality of electricallyconductive filaments, wherein the fluid permeable heater assemblyextends across the opening of the housing of the liquid storage portion.

A cartridge with this construction may be made robust, reliable and atlow cost. The heater assembly may be substantially flat, without theneed for any winding of a heater wire around a capillary wick.

The electrically conductive filaments may lie in a single plane. Aplanar heater assembly can be easily handled during manufacture andprovides for a robust construction.

The electrically conductive filaments may define interstices between thefilaments and the interstices may have a width of between 10 μm and 100μm. Preferably the filaments give rise to capillary action in theinterstices, so that in use, liquid to be vapourised is drawn into theinterstices, increasing the contact area between the heater assembly andthe liquid.

The electrically conductive filaments may form a mesh of size between160 and 600 Mesh US (+/−10%) (i.e. between 160 and 600 filaments perinch (+/−10%)). The width of the interstices is preferably between 75 μmand 25 μm. The percentage of open area of the mesh, which is the rationof the area of the interstices to the total area of the mesh ispreferably between 25 and 56%. The mesh may be formed using differenttypes of weave or lattice structures. Alternatively, the electricallyconductive filaments consist of an array of filaments arranged parallelto one another.

The electrically conductive filaments may have a diameter of between 10μm and 100 μm, preferably between 8 μm and 50 μm, and more preferablybetween 8 μm and 39 μm. The filaments may have a round cross section ormay have a flattened cross-section. The heater filaments may be formedby etching a sheet material, such as a foil. This may be particularlyadvantageous when the heater assembly comprises an array of parallelfilaments. If the heater assembly comprises a mesh or fabric offilaments, the filaments may be individually formed and knittedtogether.

The area of the mesh, array or fabric of electrically conductivefilaments may be small, preferably less than or equal to 25 mm²,allowing it to be incorporated in to a handheld system. The mesh, arrayor fabric of electrically conductive filaments may, for example, berectangular and have dimensions of 5 mm by 2 mm. Preferably, the mesh orarray of electrically conductive filaments covers an area of between 10%and 50% of the area of the heater assembly. More preferably, the mesh orarray of electrically conductive filaments covers an area of between 15and 25% of the area of the heater assembly.

The electrically conductive filaments may comprise any suitableelectrically conductive material. Preferred materials for theelectrically conductive filaments are 304, 316, 304L, 316L stainlesssteel, and graphite.

The electrical resistance of the mesh, array or fabric of electricallyconductive filaments of the heater element is preferably between 0.3 and4 Ohms. More preferably, the electrical resistance of the mesh, array orfabric of electrically conductive filaments is between 0.5 and 3 Ohms,and more preferably about 1 Ohm. The electrical resistance of the mesh,array or fabric of electrically conductive filaments is preferably atleast an order of magnitude, and more preferably at least two orders ofmagnitude, greater than the electrical resistance of the contactportions.

The housing of the liquid storage portion may contain a capillarymaterial, as described in relation to the first aspect. The capillarymaterial may be oriented in the housing to convey liquid to the heaterassembly. The capillary material may be in contact with the heaterassembly. The capillary material may extend into interstices between thefilaments.

As described in relation to the first aspect, the housing may containtwo or more different capillary materials, wherein a first capillarymaterial, in contact with the heater element, has a higher thermaldecomposition temperature and a second capillary material, in contactwith the first capillary material but not in contact with the heaterelement has a lower thermal decomposition temperature. The firstcapillary material may separate the heater assembly from the secondcapillary material by a distance of at least 1.5 mm, and preferablybetween 1.5 and 2 mm in order to provide a sufficient temperature dropacross the first capillary material.

As described in relation to the first aspect, the heater assembly maycomprise at least one filament made from a first material and at leastone filament made from a second material different from the firstmaterial.

The heater assembly may comprise an electrically insulating substrate onwhich the filaments are supported, the filaments extending across anaperture formed in the substrate. The electrically insulating substratemay comprise any suitable material, and is preferably a material that isable to tolerate high temperatures (in excess of 300° C.) and rapidtemperature changes. An example of a suitable material is a polyimidefilm, such as Kapton®.

The heater assembly may comprise an electrically conductive contact incontact with a plurality of the filaments. The electrically conductivecontact may be provided between the housing of the liquid storageportion and the electrically insulating substrate. The electricallyconductive contact may be provided between the filaments and theelectrically insulating substrate. An aperture may be formed in theelectrically insulating layer, and the cartridge may comprise twoelectrically conductive contacts positioned on opposite sides on theaperture to one another.

Advantageously, the electrically conductive contact is accessible froman exterior of the cartridge. The heater assembly may extend in alateral plane and the electrically conductive contact may extendlaterally beyond the housing of the liquid storage portion. Thecartridge may then be configured to be inserted into anaerosol-generating device in a direction orthogonal to the lateralplane, bringing the electrically conductive contact into contact with anelectrical contact on the device.

The housing of the liquid storage portion may be substantiallycylindrical, wherein the opening is at one end of the cylinder. Thehousing of the liquid storage portion may have a substantially circularcross section.

The heater assembly is advantageously covered by a removable cover orseal prior to use. The cover or seal may protect the substrate fromdegradation during storage and transport.

In a preferred embodiment the cartridge does not comprise an electricalpower source.

In a third aspect, there is provided a method of manufacture of acartridge for use in an electrically operated aerosol-generating system,comprising:

providing a liquid storage portion comprising a housing having anopening;

filling the liquid storage portion with liquid aerosol-formingsubstrate; and

fixing a fluid permeable heater assembly comprising a plurality ofelectrically conductive filaments to the liquid storage portion, whereinthe fluid permeable heater assembly extends across the opening of thehousing of the liquid storage portion.

The step of filling the liquid storage portion may be performed beforeor after the step of fixing the heater assembly to the liquid storageportion.

The step of fixing may, for example, comprise heat sealing, gluing orwelding the heater assembly to the liquid storage portion. The liquidstorage portion may contain a capillary material.

Features described in relation to one aspect may equally be applied toother aspects of the invention. In particular features described inrelation to the first aspect may equally be applied to the second aspectand the third aspect.

As used herein, “electrically conductive” means formed from a materialhaving a resistivity of 1×10⁻⁴ Ωm, or less. As used herein,“electrically insulating” means formed from a material having aresistivity of 1×10⁴ Ωm or more. As used herein “fluid permeable” inrelation to a heater assembly means that the aerosol-forming substrate,in a gaseous phase and possibly in a liquid phase, can readily passthrough the heater assembly.

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings, in which:

FIGS. 1a to 1d are schematic illustrations of a system, incorporating acartridge, in accordance with an embodiment of the invention;

FIG. 2 is a schematic illustration of a clasp mechanism for themouthpiece portion of the system of FIG. 1;

FIG. 3 is an exploded view of the cartridge of FIGS. 1a to 1 d;

FIG. 4 is an exploded view of an alternative cartridge for use in asystem as shown in FIGS. 1a to 1 d;

FIG. 5a is a perspective underside view of the cartridge of FIG. 2;

FIG. 5b is a perspective topside view of the cartridge of FIG. 2, withthe cover removed;

FIG. 6 is a detail view of a heater assembly used in the cartridge shownin FIG. 2;

FIG. 7 is a detail view of an alternative heater assembly that can beused in the cartridge shown in FIG. 2;

FIG. 8 is a detail view of a further alternative heater assembly thatcan be used in the cartridge shown in FIG. 2;

FIG. 9 is a detail view of a still further alternative heater assemblythat can be used in the cartridge shown in FIG. 2;

FIG. 10 is a detail view of alternative mechanism for making electricalcontact between the device and the heater assembly;

FIGS. 11a and 11b illustrate some cartridge housing shapes that can beused to ensure correct alignment of the cartridge in the device;

FIG. 12a is a detailed view of the filaments of the heater, showing ameniscus of liquid aerosol-forming substrate between the filaments;

FIG. 12b is a detailed view of the filaments of the heater, showing ameniscus of liquid aerosol-forming substrate between the filaments and acapillary material extending between the filaments;

FIGS. 13a, 13b and 13c illustrate alternative methods of manufacture fora heater assembly in accordance with the invention; and

FIG. 14 illustrates an alternative design for a liquid storage portionincorporating a heater assembly.

FIGS. 15a and 15b illustrate additional alternative embodiments of aliquid storage portion incorporating a heater assembly.

FIG. 16 illustrates an alternative embodiment of the airflow andcartridge orientation with the aerosol-generating device.

FIG. 17 shows a cross-section of a cartridge system with high retentionmaterial and air passage through the HRM;

FIG. 18 shows a cross-section of another cartridge system with highretention material and air passage through the cartridge;

FIG. 19 shows an exploded view of the cartridge system of FIG. 18;

FIG. 20 shows a cross-section of a cartridge system with a liquid andair passage through the liquid.

FIGS. 1a to 1d are schematic illustrations of an aerosol-generatingsystem, including a cartridge in accordance with an embodiment of theinvention. FIG. 1a is a schematic view of an aerosol-generating device10 and a separate cartridge 20, which together form theaerosol-generating system. In this example, the aerosol-generatingsystem is an electrically operated smoking system.

The cartridge 20 contains an aerosol-forming substrate and is configuredto be received in a cavity 18 within the device. Cartridge 20 should bereplaceable by a user when the aerosol-forming substrate provided in thecartridge is depleted. FIG. 1a shows the cartridge 20 just prior toinsertion into the device, with the arrow 1 in FIG. 1a indicating thedirection of insertion of the cartridge.

The aerosol-generating device 10 is portable and has a size comparableto a conventional cigar or cigarette. The device 10 comprises a mainbody 11 and a mouthpiece portion 12. The main body 11 contains a battery14, such as a lithium iron phosphate battery, control electronics 16 anda cavity 18. The mouthpiece portion 12 is connected to the main body 11by a hinged connection 21 and can move between an open position as shownin FIG. 1 and a closed position as shown in FIG. 1d . The mouthpieceportion 12 is placed in the open position to allow for insertion andremoval of cartridges 20 and is placed in the closed position when thesystem is to be used to generate aerosol, as will be described. Themouthpiece portion comprises a plurality of air inlets 13 and an outlet15. In use, a user sucks or puffs on the outlet to draw air from the airinlets 13, through the mouthpiece portion to the outlet 15, andthereafter into the mouth or lungs of the user. Internal baffles 17 areprovided to force the air flowing through the mouthpiece portion 12 pastthe cartridge, as will be described.

The cavity 18 has a circular cross-section and is sized to receive ahousing 24 of the cartridge 20. Electrical connectors 19 are provided atthe sides of the cavity 18 to provide an electrical connection betweenthe control electronics 16 and battery 14 and corresponding electricalcontacts on the cartridge 20.

FIG. 1b shows the system of FIG. 1a with the cartridge inserted into thecavity 18, and the cover 26 being removed. In this position, theelectrical connectors rest against the electrical contacts on thecartridge, as will be described.

FIG. 1c shows the system of FIG. 1b with the cover 26 fully removed andthe mouthpiece portion 12 being moved to a closed position.

FIG. 1d shows the system of FIG. 1c with the mouthpiece portion 12 inthe closed position. The mouthpiece portion 12 is retained in the closedposition by a clasp mechanism, as is schematically illustrated in FIG.2. FIG. 2 illustrates the main body 11 and mouthpiece portion 12connected by hinged connection 21. The mouthpiece portion 12 comprisesan inwardly extending tooth 8. When the mouthpiece portion is in aclosed position, the tooth 8 engages a clasp 6 on the main body of thedevice. The clasp 6 is biased by biasing spring 5 to engage the tooth 8.A button 4 is fixed to the clasp 6. Button 4 can be depressed by a useragainst the action of the biasing spring 5 to release the tooth 8 fromthe clasp 6, allowing the mouthpiece portion to move to an openposition. It will now be apparent to a person of ordinary skill in theart that other suitable mechanisms for retaining the mouthpiece in aclosed position may be used, such as a snap fitting or a magneticclosure.

The mouthpiece portion 12 in a closed position retains the cartridge inelectrical contact with the electrical connectors 19 so that a goodelectrical connection is maintained in use, whatever the orientation ofthe system is. The mouthpiece portion 12 may include an annularelastomeric element that engages a surface of the cartridge and iscompressed between a rigid mouthpiece housing element and the cartridgewhen the mouthpiece portion 12 is in the closed position. This ensuresthat a good electrical connection is maintained despite manufacturingtolerances.

Of course other mechanisms for maintaining a good electrical connectionbetween the cartridge and the device may, alternatively or in addition,be employed. For example, the housing 24 of the cartridge 20 may beprovided with a thread or groove (not illustrated) that engages acorresponding groove or thread (not illustrated) formed in the wall ofthe cavity 18. A threaded engagement between the cartridge and devicecan be used to ensure the correct rotational alignment as well asretaining the cartridge in the cavity and ensuring a good electricalconnection. The threaded connection may extend for only half a turn orless of the cartridge, or may extend for several turns. Alternatively,or in addition, the electrical connectors 19 may be biased into contactwith the contacts on the cartridge, as will be described with referenceto FIG. 8.

FIG. 3 is an exploded view of the cartridge 20. The cartridge 20comprises a generally circular cylindrical housing 24 that has a sizeand shape selected to be received into the cavity 18. The housingcontains a capillary material 22 that is soaked in a liquidaerosol-forming substrate. In this example the aerosol-forming substratecomprises 39% by weight glycerine, 39% by weight propylene glycol, 20%by weight water and flavourings, and 2% by weight nicotine. A capillarymaterial is a material that actively conveys liquid from one end toanother, and may be made from any suitable material. In this example thecapillary material is formed from polyester.

The housing has an open end to which a heater assembly 30 is fixed. Theheater assembly 30 comprises a substrate 34 having an aperture 35 formedin it, a pair of electrical contacts 32 fixed to the substrate andseparated from each other by a gap 33, and a plurality of electricallyconductive heater filaments 36 spanning the aperture and fixed to theelectrical contacts on opposite sides of the aperture 35.

The heater assembly 30 is covered by a removable cover 26. The covercomprises a liquid impermeable plastic sheet that is glued to the heaterassembly but which can be easily peeled off. A tab is provided on theside of the cover to allow a user to grasp the cover when peeling itoff. It will now be apparent to one of ordinary skill in the art thatalthough gluing is described as the method to a secure the impermeableplastic sheet to the heater assembly, other methods familiar to those inthe art may also be used including heat sealing or ultrasonic welding,so long as the cover may easily be removed by a consumer.

FIG. 4 is an exploded view of an alternative exemplary cartridge. Thecartridge of FIG. 4 is the same size and shape as the cartridge of FIG.3 and has the same housing and heater assembly. However, the capillarymaterial within the cartridge of FIG. 4 is different to that of FIG. 3.There are two separate capillary materials 27, 28 in the cartridge ofFIG. 4. A disc of a first capillary material 27 is provided to contactthe heater element 36, 32 in use. A larger body of a second capillarymaterial 28 is provided on an opposite side of the first capillarymaterial 27 to the heater assembly. Both the first capillary materialand the second capillary material retain liquid aerosol-formingsubstrate. The first capillary material 27, which contacts the heaterelement, has a higher thermal decomposition temperature (at least 160°C. or higher such as approximately 250° C.) than the second capillarymaterial 28. The first capillary material 27 effectively acts as aspacer separating the heater element 36, 32 from the second capillarymaterial 28 so that the second capillary material is not exposed totemperatures above its thermal decomposition temperature. The thermalgradient across the first capillary material is such that the secondcapillary material is exposed to temperatures below its thermaldecomposition temperature. The second capillary material 28 may bechosen to have superior wicking performance to the first capillarymaterial 27, may retain more liquid per unit volume than the firstcapillary material and may be less expensive than the first capillarymaterial. In this example the first capillary material is a heatresistant material, such as a fiberglass or fiberglass containingmaterial and the second capillary material is a polymer such as suitablecapillary material. Exemplary suitable capillary materials include thecapillary materials discussed herein and in alternative embodiments mayinclude high density polyethylene (HDPE), or polyethylene terephthalate(PET).

FIG. 5a is a perspective underside view of the cartridge of FIG. 3. Itcan be seen from FIG. 5a that the heater assembly extends in a lateralplane and extends laterally beyond the housing 24 so that the heaterassembly forms a lip around the top of the housing 24. Exposed portionsof the electrical contacts 32 face in an insertion direction of thecartridge so that when the cartridge is fully inserted into the cavity18, the exposed portions of the contacts 32 contact the electricalconnectors 19. The tab, provided on the side of the cover 26 to allow auser to grasp the cover when peeling it off, can be clearly seen. FIG.5a also illustrates a locating portion 25 formed on the base of thecartridge for ensuring the correct orientation of the cartridge in thecavity of the device. The locating portion 25 is part of the injectionmoulded housing 24 and is configured to be received in a correspondingslot (not illustrated) in the base of the cavity 18. When the locatingportion 25 is received in the slot in the cavity, the contacts 32 arealigned with the connectors 19.

FIG. 5b is a perspective topside view of the cartridge of FIG. 3, withthe cover removed. The heater filaments 36 are exposed through theaperture 35 in the substrate 34 so that vapourised aerosol-formingsubstrate can escape into the air flow past the heater assembly.

The housing 24 is formed from a thermoplastic, such as polypropylene.The heater assembly 30 is glued to the housing 24 in this example.However, there are several possible ways in which to assembly and fillthe cartridge.

The cartridge housing may be formed by injection moulding. The capillarymaterials 22, 27, 28 may be formed by cutting suitable lengths ofcapillary material from a long rod of capillary fibres. The heaterassembly may be assembled using a process as described with reference toFIGS. 11a, 11b and 11c . In one embodiment the cartridge is assembled byfirst inserting the one or more capillary materials 22, 27, 28 into thehousing 24. A predetermined volume of liquid aerosol-forming substrateis then introduced into the housing 24, soaking the capillary materials.The heater assembly 30 is then pushed onto the open end of the housingand fixed to the housing 24 by gluing, welding, heat sealing, ultrasonicwelding, or other methods that will now be apparent to one of ordinaryskill in the art. The temperature of the housing is preferably heldbelow 160° C. during any sealing operation to prevent unwantedvolatising of the aerosol-forming substrate. The capillary material maybe cut to a length such that it extends out of the open end of thehousing 24 until it is compressed by the heater assembly. This promotestransport of aerosol-forming substrate into the interstices of theheater element in use.

In another embodiment, instead of pressing the heater assembly 30 ontothe housing 24 and then sealing, the heater assembly and the open end ofthe housing may first be flash heated and then pressed together to bondthe heater assembly 30 to the housing 24.

It is also possible to assemble the heater assembly 30 to the housing 24before filling the housing with aerosol-forming substrate andsubsequently to introduce the aerosol-forming substrate in to thehousing 24. In that case, the heater assembly may be fixed to thecartridge using any of the methods described. The heater assembly orhousing is then pierced using a hollow needle and the aerosol-formingsubstrate injected into the capillary material 22, 27, 28. Any openingmade by the hollow needle is then sealed by heat sealing or by using asealing tape.

FIG. 6 is an illustration of a first heater assembly 30 in accordancewith the disclosure. The heater assembly comprises a mesh formed from304L stainless steel, with a mesh size of about 400 Mesh US (about 400filaments per inch). The filaments have a diameter of around 16 μm. Themesh is connected to electrical contacts 32 that are separated from eachother by a gap 33 and are formed from a copper foil having a thicknessof around 30 μm. The electrical contacts 32 are provided on a polyimidesubstrate 34 having a thickness of about 120 μm. The filaments formingthe mesh define interstices between the filaments. The interstices inthis example have a width of around 37 μm, although larger or smallerinterstices may be used. Using a mesh of these approximate dimensionsallows a meniscus of aerosol-forming substrate to be formed in theinterstices, and for the mesh of the heater assembly to drawaerosol-forming substrate by capillary action. The open area of themesh, i.e. the ratio of the area of interstices to the total area of themesh is advantageously between 25 and 56%. The total resistance of theheater assembly is around 1 Ohm. The mesh provides the vast majority ofthis resistance so that the majority of the heat is produced by themesh. In this example the mesh has an electrical resistance more than100 times higher than the electrical contacts 32.

The substrate 34 is electrically insulating and, in this example, isformed from a polyimide sheet having a thickness of about 120 μm. Thesubstrate is circular and has a diameter of 8 mm. The mesh isrectangular and has side lengths of 5 mm and 2 mm.

These dimensions allow for a complete system having a size and shapesimilar to a convention cigarette or cigar to be made. Another exampleof dimensions that have been found to be effective is a circularsubstrate of diameter 5 mm and a rectangular mesh of 1 mm×4 mm.

FIG. 7 is an illustration of an alternative, exemplary heater assemblyin accordance with the disclosure. The heater assembly of FIG. 7 is thesame as that shown in FIG. 6 but the mesh 36 is replaced by an array ofparallel electrically conductive filaments 37. The array of filaments 37are formed from 304L stainless steel and have a diameter of around 16μm. The substrate 34 and copper contact 32 are as described withreference to FIG. 6.

FIG. 8 is an illustration of another alternative heater assembly inaccordance with the disclosure. The heater assembly of FIG. 8 is thesame as that shown in FIG. 7 but in the assembly of FIG. 8, thefilaments 37 are bonded directly to the substrate 34 and the contacts 32are then bonded onto the filaments. The contacts 32 are separated fromeach other by insulating gap 33 as before, and are formed from copperfoil of a thickness of around 30 μm. The same arrangement of substratefilaments and contacts can be used for a mesh type heater as shown inFIG. 6. Having the contacts as an outermost layer can be beneficial forproviding reliable electrical contact with a power supply.

FIG. 9 is an illustration of an alternative heater assembly inaccordance with the disclosure. The heater assembly of FIG. 9 comprisesa plurality of heater filaments 38 that are integrally formed withelectrical contacts 39. Both the filaments and the electrical contactsare formed from a stainless steel foil that is etched to definefilaments 38. The contacts 39 are separated by a gap 33 except whenjoined by filaments 38. The stainless steel foil is provided on apolyimide substrate 34. Again the filaments 38 provide the vast majorityof this resistance, so that the majority of the heat is produced by thefilaments. In this example the filaments 38 have an electricalresistance more than 100 times higher than the electrical contacts 39.

In the cartridge shown in FIGS. 3, 4 and 5, the contacts 32 andfilaments 36, 38 are located between the substrate layer 34 and thehousing 24. However, it is possible to mount the heater assembly to thecartridge housing the other way up, so that the polyimide substrate isdirectly adjacent to the housing 24. FIG. 10 illustrates an arrangementof this type. FIG. 10 shows a heater assembly comprising a stainlesssteel mesh 56, fixed to copper foil contacts 52. The copper contacts 52are fixed to a polyimide substrate 54. An aperture 55 is formed in thepolyimide substrate 54. The polyimide substrate is welded to the housing24 of the cartridge. A capillary material 22, soaked in aerosol-formingsubstrate, fills the housing and extends through the aperture to contactthe mesh 55. The cartridge is shown received in the main body 11 of thedevice and held between electrical connectors 59 and mouthpiece portion12. In this embodiment, in order for the electrical connectors 59 tomake an electrical connection with the contacts 52, the connectors 59are adapted to pierce the polyimide substrate 54, as shown. Theelectrical connectors are made with sharpened ends and are urged intocontact with the heater assembly by springs 57. The polyimide substratemay be pre-scored to ensure a good electrical contact is made, or mayeven be provided with apertures so that piercing of the substrate is notnecessary. The springs 57 also ensure that a good electrical contactbetween the contacts 52 and the connectors 59 is maintained whatever theorientation of the system with respect to gravity.

One means for ensuring the correct orientation of the cartridge 20 inthe cavity 18 of the device has been described with reference to FIGS.5a and 5b . The locating portion 25 can be formed as part of the mouldedcartridge housing 24 to ensure the correct orientation. However, it willbe apparent that other ways of ensuring the correct orientation of thecartridge are possible. In particular, if the housing is injectionmoulded, there are almost limitless possibilities for the shape of thecartridge. Once the desired internal volume of the cartridge has beenchosen, the cartridge shape can be adapted to suit any cavity. FIG. 11ais a base view of one possible cartridge housing 70, allowing thecartridge to be oriented in two possible orientations. The cartridgehousing 70 includes two symmetrically disposed, grooves 72. The groovesmay extend partially or fully up the side of the housing 70.Corresponding ribs (not illustrated) may be formed on the walls of thecavity of the device, so that the cartridge can be received in thecavity in only two possible orientations. In the embodiment of FIG. 11ait is possible to have only a single rib in the cavity so that one ofthe grooves 72 is not filled by a rib and can be used as an air flowchannel within the device. It is of course possible to restrict thecartridge to a single orientation within the cavity by providing only asingle groove in the housing. This is illustrated in FIG. 11b , whichshows a cartridge housing 74 with a single groove 76.

Although the embodiments described have cartridges with housings havinga substantially circular cross section, it is of course possible to formcartridge housings with other shapes, such as rectangular cross sectionor triangular cross section. These housing shapes would ensure a desiredorientation within the corresponding shaped cavity, to ensure theelectrical connection between the device and the cartridge.

The capillary material 22 is advantageously oriented in the housing 24to convey liquid to the heater assembly 30. When the cartridge isassembled, the heater filaments 36, 37,38 may be in contact with thecapillary material 22 and so aerosol-forming substrate can be conveyeddirectly to the mesh heater. FIG. 12a is a detailed view of thefilaments 36 of the heater assembly, showing a meniscus 40 of liquidaerosol-forming substrate between the heater filaments 36. It can beseen that aerosol-forming substrate contacts most of the surface of eachfilament so that most of the heat generated by the heater assemblypasses directly into the aerosol-forming substrate. In contrast, inconventional wick and coil heater assemblies only a small fraction ofthe heater wire is in contact with the aerosol-forming substrate. FIG.12b is a detailed view, similar to FIG. 12a , showing an example of acapillary material 27 that extends into the interstices between thefilaments 36. The capillary material 27 is the first capillary materialshown in FIG. 4. It can be seen that by providing a capillary materialcomprising fine threads of fibres that extend into the intersticesbetween the filaments 36, transport of liquid to the filaments can beensured. In use the heater assembly operates by resistive heating.Current is passed through the filaments 36, 37 38, under the control ofcontrol electronics 16, to heat the filaments to within a desiredtemperature range. The mesh or array of filaments has a significantlyhigher electrical resistance than the electrical contacts 32 andelectrical connectors 19 so that the high temperatures are localised tothe filaments. The system may be configured to generate heat byproviding electrical current to the heater assembly in response to auser puff or may be configured to generate heat continuously while thedevice is in an “on” state. Different materials for the filaments may besuitable for different systems. For example, in a continuously heatedsystem, graphite filaments are suitable as they have a relatively lowspecific heat capacity and are compatible with low current heating. In apuff actuated system, in which heat is generated in short bursts usinghigh current pulses, stainless steel filaments, having a high specificheat capacity may be more suitable.

In a puff actuated system, the device may include a puff sensorconfigured to detect when a user is drawing air through the mouthpieceportion. The puff sensor (not illustrated) is connected to the controlelectronics 16 and the control electronics 16 are configured to supplycurrent to the heater assembly 30 only when it is determined that theuser is puffing on the device. Any suitable air flow sensor may be usedas a puff sensor, such as a microphone.

In a possible embodiment, changes in the resistivity of one or more ofthe filaments 36, 38 or of the heater element as a whole may be used todetect a change in the temperature of the heater element. This can beused to regulate the power supplied to the heater element to ensure thatit remains within a desired temperature range. Sudden changes intemperature may also be used as a means to detect changes in air flowpast the heater element resulting from a user puffing on the system. Oneor more of the filaments may be dedicated temperature sensors and may beformed from a material having a suitable temperature coefficient ofresistance for that purpose, such as an iron aluminium alloy, Ni—Cr,platinum, tungsten or alloy wire.

The air flow through the mouthpiece portion when the system is used isillustrated in FIG. 1d . The mouthpiece portion includes internalbaffles 17, which are integrally moulded with the external walls of themouthpiece portion and ensure that, as air is drawn from the inlets 13to the outlet 15, it flows over the heater assembly 30 on the cartridgewhere aerosol-forming substrate is being vapourised. As the air passesthe heater assembly, vapourised substrate is entrained in the airflowand cools to form an aerosol before exiting the outlet 15. Accordingly,in use, the aerosol-forming substrate passes through the heater assemblyby passing through the interstices between the filaments 36, 37, 38 asit is vapourised.

There are a number of possibilities for manufacture and for thematerials of the heater assembly. FIG. 13a is a schematic illustrationof a first method of manufacture of a heater assembly. A roll ofpolyimide film 80 is provided with an array of apertures 82 in it. Theapertures 82 may be formed by stamping. Bands of copper foil 84 areplated onto the polyimide film 80 between the apertures. Ribbons ofstainless steel mesh 86 are then clad onto the polyimide film 80 on topof the copper foil 84 and over the apertures 82 in a directionorthogonal to the bands of copper foil. Individual heater assemblies 30can then be cut or stamped out around each aperture 82. Each heaterassembly 30 includes a portion of copper foil on opposite sides of theaperture, forming electrical contacts, and a strip of stainless steelmesh spans the aperture from one portion of copper to the other, asshown in FIG. 6.

FIG. 13b illustrates another possible manufacturing process. In theprocess of FIG. 13b a polyimide film 80 of the type used in the processof FIG. 13a , is clad with stainless steel foil 90. The polyimide film80 has an array of apertures 82 formed in it but these apertures arecovered by the stainless steel foil 90. The foil 90 is then etched todefine filaments 38 spanning the apertures 82 and separate contactportions on opposite sides of the apertures. Individual heaterassemblies 92 can then be cut or stamped out around each aperture 82.This provides a heater assembly of the type shown in FIG. 9.

FIG. 13c illustrates a further alternative process. In the process ofFIG. 13c a graphite based fabric 100 is first prepared. The graphitebased fabric 100 comprises bands of electrically resistive fibres,suitable for use as heater filaments, adjacent bands of relativelynon-conductive fibres. These bands of fibres are woven together withbands of relatively electrically conductive fibres that extendperpendicular to the resistive and non-conductive fibres. This fabric100 is then bonded to a layer of polyimide film 80 of the type describedwith reference to FIGS. 13a and 13b , having an array of apertures 82.Individual heater assemblies 102 can then be cut or stamped out aroundeach aperture. Each heater assembly 102 includes a portion of a band ofconductive fibres on opposite sides of the aperture and a band ofelectrically resistive fibres span the aperture.

The cartridge design shown in FIGS. 5a and 5b has several advantages.However, alternative cartridge designs using the same type of heaterassembly are possible. FIG. 14 illustrates an alternative cartridgedesign that is suited to a different pattern of airflow through thesystem. In the embodiment shown in FIG. 14, the cartridge 108 isconfigured to be inserted into the device in the direction indicated bythe arrow 110. The cartridge 108 comprises a housing 112 which is shapedlike a half cylinder and is open one side. A heater assembly 114 isprovided across the open side and is glued or welded to the housing 112.The heater assembly 114 comprises an electrically insulating substrate116, such as polyimide having an aperture formed in it. A heater elementcomprising a stainless steel mesh 118 and a pair of contact strips 120is bonded to the electrically insulating substrate 116 and spans theaperture. The contact strips 120 are bent around the housing 112 to formcontact pads on a curved surface of the housing. The electrical contactpads are configured to contact corresponding contacts (not illustrated)in the aerosol-generating device. The housing 112 is filled with acapillary material (not visible in FIG. 14) soaked in aerosol-formingsubstrate, as described with reference to the embodiment shown in FIGS.1a to 1 d.

The cartridge shown in FIG. 14 is configured for airflow past the heaterassembly 114 in a direction opposite to arrow 110. Air is drawn into thesystem through an air inlet provided in a main body of the device and issucked past the heater assembly 114, into a mouthpiece portion of thedevice (or cartridge) and into a user's mouth. Air drawn into the systemmay be directed, for example, in a direction parallel along mesh 118 byappropriate placement of air inlets.

Alternative embodiments of the cartridge 108 are illustrated in FIGS.15a and 15b . FIG. 15a further includes contract strips 120 spaced apartand running the length of the face having mesh 118. FIG. 15b furtherincludes contacts 120 having roughly an L shape. Both cartridge designsillustrated in FIGS. 15a and 15b may be used to provide even largercontact areas to further ensure easy contact to contacts 19 if required.Strips 120 as illustrated in FIG. 15a may also configured to be slideinto a contact 19 that is configured in a rail configuration (notillustrated) for receiving strips 120 to further position the cartridge.Such a rail-type configuration may advantageously provide a periodiccleaning of the contacts 19 as the insertion and removal of thecartridge will have a cleaning effect based on the friction of thecontact sliding in and out of the rails.

FIG. 16 illustrates yet another embodiment of an aerosol-generatingsystem comprising a fluid-permeable electric heater assembly. FIG. 16illustrates system where the heater assembly 30 is provided at an end ofthe cartridge 20 that is opposite to the mouthpiece portion 12. Airflowenters an air inlet 1601 and passes by the assembly and through an airoutlet 1603 along a flow route 1605. Electrical contacts may be placedin any convenient location. Such a configuration is advantageous as itallows for shorter electrical connections within the system.

Other cartridge designs incorporating a heater assembly in accordancewith this disclosure can now be conceived by one of ordinary skill inthe art. For example, the cartridge may include a mouthpiece portion,may include more than one heater assembly and may have any desiredshape. Furthermore, a heater assembly in accordance with the disclosuremay be used in systems of other types to those already described, suchas humidifiers, air fresheners, and other aerosol-generating systems

The exemplary embodiments described above illustrate but are notlimiting. In view of the above discussed exemplary embodiments, otherembodiments consistent with the above exemplary embodiments will now beapparent to one of ordinary skill in the art.

In FIG. 17 a cross section of a cartridge system, wherein a flow routecomprises an airflow directed through the cartridge is illustrated. Afluid permeable heater, for example a mesh heater 30, compriseselectrically conductive heater filaments 36 spanning the aperture of thehousing 400. For sealing the top of the housing 400, a sealing layer 48,for example a polymer layer, is provided between the upper rim of thehousing 400 and the heater 30. In addition, a sealing disc 47, forexample a polymer disc, is provided on the top side of the heater 30.With the sealing disc 47 airflow through the heater may be controlled,in particular, airflow constraints may be provided. The sealing disc mayalso be arranged on the bottom side of the heater 30.

The cartridge housing 400 comprises a liquid containing capillarymaterial such as a high retention material or high release material(HRM) 41 serving as liquid reservoir and directing liquid towards theheater 30 for evaporation at the heater. Another capillary material, acapillary disc 44, for example a fiber disc, is arranged between HRM 41and heater 30. The material of the capillary disc 44 may be more heatresistant than the HRM 41 due to its closeness to the heater 30. Thecapillary disc is kept wet with the aerosol-forming liquid of the HRM tosecure provision of liquid for vaporization if the heater is activated.

The housing 400 is provided with an air permeable bottom 45. The airpermeable bottom is provided with an airflow inlet 450. The airflowinlet 450 allows air to flow through the bottom 45 into the housing inone and this direction only. No air or liquid may leave the housingthrough the air permeable bottom 45. The air permeable bottom 45 may forexample comprise a semi-permeable membrane as airflow inlet 450 or maybe a bottom cover comprising one or more one-way valves as will be shownbelow.

If low depression prevails on the side of the heater, as is the caseduring puffing, air may pass through the airflow inlet 450 into thecartridge. The airflow 200 will pass through the HRM 41 and through theheater 30. The aerosol containing airflow 200 will then flow to adownstream end of the aerosol generating device, preferably in acentrally arranged channel in a mouthpiece.

Side walls of the housing 400 may also be provided with lateral airpermeable sections 46 for providing later airflows into the housing.Lateral air permeable sections 46 may be designed as the airflow inlets450 in the air permeable bottom 45.

In FIG. 18 the arrangement and function of the cartridge system isbasically the same as shown in FIG. 10. However, the HRM 41 is providedwith a central opening 412. Air entering the airflow inlet 450 in thebottom 45 of the housing passes through the central opening 412. Theairflow passes next to the HRM in the cartridge. With optional lateralair permeable sections 46 in the side wall of the housing 400, lateralairflow may be provided through the HRM 41.

In FIG. 19 an exploded view of cartridge system as in FIG. 11 is shown.A ring-shaped tubular HRM 41 is provided in the housing 400. The bottom45 of the housing is a disc comprising a one-way valve 49 arranged inthe centre of the disc and aligned with the central opening 412 in theHRM 41. Such a one-way valve may for example be a commercially availablevalve, such as for example used in medical devices or in baby bottles.

FIG. 20 is a cross section of another embodiment of a cartridge system.Same reference numerals are used for the same or similar elements. Inthis embodiment, the housing 400 is filled with an aerosol-formingliquid 411. The housing may be made of metal, plastics material, forexample a polymeric material, or glass. The valve 49 may directly bemoulded into the bottom 45 of the housing. The bottom 45 may also beprovided with a cavity for air-tight assembly with the valve. Due to thevalves preferably being made of a flexible material, tight assembly withthe bottom material may be achieved.

In the above cartridge systems as described in FIG. 17 to FIG. 20 thecartridge housing 400 may also be a separate cartridge container inaddition to the cartridge housing as described for example in FIG. 1.Especially, a liquid 411 containing cartridge is a pre-manufacturedproduct, which may be inserted into a cartridge housing provided in theaerosol generating system for receiving the pre-manufactured cartridge.

1. An aerosol-generating system, comprising: a liquid storage portioncomprising a housing holding a liquid aerosol-forming substrate, thehousing having an opening; and a fluid permeable heater assemblycomprising a substantially flat electrically conductive filamentarrangement, wherein the fluid permeable heater assembly is fixed to thehousing and extends across the opening of the housing, wherein an areaof the electrically conductive filament arrangement is less than orequal to 25 mm².
 2. The aerosol-generating system according to claim 1,wherein the fluid permeable heater assembly is substantially flat. 3.The aerosol generating system according to claim 2, further comprising acapillary medium, wherein the capillary medium is substantially a samesize and shape as the fluid permeable heater assembly, and the capillarymedium is provided in contact with the fluid permeable heater assembly,and wherein the liquid aerosol-forming substrate is drawn via thecapillary medium to the electrically conductive filament arrangement. 4.The aerosol-generating system according to claim 1, further comprising amain unit and a cartridge that is removably coupled to the main unit,wherein the liquid storage portion and the fluid permeable heaterassembly are provided in the cartridge and the main unit comprises apower supply.
 5. The aerosol-generating system according to claim 1,wherein the the electrically conductive filament arrangement forms amesh.
 6. The aerosol-generating system according to claim 1, wherein theelectrically conductive filament arrangement consists of a plurality offilaments arranged parallel to one another.
 7. The aerosol-generatingsystem according to claim 3, wherein the capillary medium extends intointerstices between filaments of the electrically conductive filamentarrangement.
 8. The aerosol-generating system according to claim 7,wherein the capillary medium includes a first capillary material and asecond capillary material, the first capillary material being in contactwith the fluid permeable heater assembly, and the second capillarymaterial being in contact with the first capillary material and spacedapart from the fluid permeable heater assembly by the first capillarymaterial, and wherein the first capillary material has a higher thermaldecomposition temperature than the second capillary material.
 9. Theaerosol generating system according to claim 8, wherein the secondcapillary material retains between 20-160 mg of the liquidaerosol-forming substrate.
 10. The aerosol-generating system accordingto claim 9, wherein the higher thermal decomposition temperature of thefirst capillary material is at least 160° C.
 11. The aerosol-generatingsystem according to claim 1, wherein the substantially flat electricallyconductive filament arrangement of the fluid permeable heater assemblyfurther comprises at least one filament made from a first material andat least one filament made from a second material different from thefirst material.
 12. The aerosol-generating system according to claim 1,further comprising electric circuitry connected to the fluid permeableheater assembly and to an electrical power source, the electriccircuitry being configured to monitor an electrical resistance of thefluid permeable heater assembly or of one or more filaments of thesubstantially flat electrically conductive filament arrangement of thefluid permeable heater assembly, and to control a supply of power fromthe electrical power source to the fluid permeable heater assemblydependent on the electrical resistance of the fluid permeable heaterassembly or of the one or more filaments.
 13. The aerosol-generatingsystem according to claim 1, wherein the fluid permeable heater assemblyfurther comprises an electrically insulating substrate on which theelectrically conductive filament arrangement is supported.
 14. Theaerosol-generating system according to claim 1, wherein the fluidpermeable heater assembly further comprises an electrically conductivecontact in contact with the electrically conductive filamentarrangement.
 15. The aerosol-generating system according to claim 1,wherein the system is an electrically operated smoking system.
 16. Acartridge for use in an electrically operated aerosol-generating system,comprising: a liquid storage portion comprising a rigid housing holdinga liquid aerosol-forming substrate, the housing having an opening; and afluid permeable heater assembly comprising a plurality of electricallyconductive filaments, wherein the fluid permeable heater assembly isfixed to the housing and extends across the opening of the housing. 17.The cartridge according to claim 16, wherein the fluid permeable heaterassembly is substantially flat.
 18. The cartridge according to claim 16,wherein the plurality of electrically conductive filaments forms a mesh.19. The cartridge according to claim 16, wherein filaments of theplurality of electrically conductive filaments consists of a pluralityof filaments are arranged parallel to one another.
 20. The cartridgeaccording to claim 16, wherein the rigid housing of the liquid storageportion contains a capillary material.
 21. The cartridge according toclaim 20, wherein the capillary material extends into intersticesbetween filaments of the plurality of electrically conductive filaments.22. The cartridge according to claim 20, wherein the capillary materialincludes a first capillary material and a second capillary material, thefirst capillary material being in contact with the fluid permeableheater assembly, and the second capillary material being in contact withthe first capillary material and spaced apart from the fluid permeableheater assembly by the first capillary material, and wherein the firstcapillary material has a higher thermal decomposition temperature thanthe second capillary material.
 23. The cartridge according to claim 16,wherein the plurality of electrically conductive filaments of the fluidpermeable heater assembly further comprises at least one filament madefrom a first material and at least one filament made from a secondmaterial different from the first material.
 24. The cartridge accordingto claim 16, wherein the fluid permeable heater assembly furthercomprises an electrically insulating substrate on which the plurality ofelectrically conductive filaments is supported, the filaments extendingacross an aperture formed in the liquid aerosol-forming substrate. 25.The cartridge according to claim 16, wherein the fluid permeable heaterassembly further comprises an electrically conductive contact in contactwith filaments of the plurality of electrically conductive filaments.26. The cartridge according to claim 25, wherein the fluid permeableheater assembly extends in a lateral plane, and wherein the electricallyconductive contact extends laterally beyond the rigid housing of theliquid storage portion.
 27. A method of manufacture of a cartridge foruse in an electrically operated aerosol-generating system, comprising:providing a liquid storage portion comprising a housing having anopening; filling the liquid storage portion with liquid aerosol-formingsubstrate; and fixing a fluid permeable heater assembly comprising aplurality of electrically conductive filaments to the liquid storageportion, wherein the fluid permeable heater assembly extends across theopening of the housing of the liquid storage portion.